The aluminum alloy wheel is provided with a flange weight reduction pit and a flange drainage channel in a flange face, one end of the flange drainage channel communicates with a central hole of the wheel, the other end of the flange drainage channel communicates with the outer edge of the flange face, the drainage channel is narrow and deep, a large amount of aluminum scraps which are generally strip-shaped, block-shaped and curly are generated in high-speed rotation of the wheel during machining, and these aluminum scraps easily splatter and are just blocked in the flange drainage channel. Since the drainage channel is narrow and deep, once the aluminum scraps are blocked, they are difficult to drop naturally and remain in the flange drainage channel. When manual operation is adopted for machining, if an operator discovers aluminum scraps blocked in the flange drainage channel, he would manually clean them. However, with the improvement on automation level, production lines of manipulators' automatic operation are gradually replacing the manual operation. As for a full-manipulator automatic production line, if aluminum scraps are blocked in the flange drainage channel, the aluminum scraps remain all the time in the absence of inspection of manipulators and manual cleaning of operators and finally result in rejects after coating, and even the rejects are circulated to customers to cause complaints.